The invention relates to methods and apparatus for cooling a hot gas exiting a gasification reactor vessel at temperatures in excess of 1300xc2x0 C., wherein the gas comes into contact with corrosive aqueous liquid.
Related inventions include a prior patent application for a Method and Apparatus for the Production of One or More Useful Products from Lesser Value Halogenated Materials, PCT international application PCT/US/98/26298, published Jul. 1, 1999, international publication number WO 99/32937. The PCT application discloses processes and apparatus for converting a feed that is substantially comprised of halogenated materials, especially by-product and waste chlorinated hydrocarbons as they are produced from a variety of chemical manufacturing processes, to one or more xe2x80x9chigher value productsxe2x80x9d via a partial oxidation reforming step in a gasification reactor. Other related inventions include six co-filed applications for certain other aspects of processes for gasifying materials, the aspects including methods and apparatus for increasing efficiencies, reactor vessel design, reactor feed nozzle designs, producing high quality acids, particulate removal and control of aerosols.
In the reformation of materials, gases tend to exit a reactor, or gasifier, at high temperatures, such as at approximately 1400xc2x0 C. to 1450xc2x0 C. Cooling of these gases preferably takes place in a subsequent quench area. Quenching is advantageously achieved in a single contacting step. In such a step preferably a recirculated, cooled aqueous liquid vigorously contacts the hot gases to effect the desired cooling. This contacting step is more preferably performed in a weir quench. The aqueous liquid, as well as the gas, may be corrosive.
A weir quench, in preferred embodiments, is a vessel having one or more short vertical weir cylinder(s) that penetrate a lower flat plate. The lower flat plate forms a partition between an upper and a lower chamber. Quench liquor flows into an annular volume created between side vessel walls and the central cylinder(s), and above the flat plate. The liquor preferably is managed to continually overflow the top of the cylinder(s) and to flow down the inside walls of the cylinder(s). When, simultaneously, a hot gas is directed to flow down through the vessel and through the cylinder(s), into a region below, the co-flow of liquid and the gas, with liquid evaporating as it cools the gas, creates an intimate mixing and cooling of the gas stream. An inventory of liquid around the weir, in such an embodiment, can serve as a reservoir in the event of a temporary interruption of liquid flow.
Liquid overflow of weir quench, as discussed above, can operate in one of three stages, with the middle stage being preferable. In a first stage, a low liquid flow rate could be insufficient to fully wet the ID wall of the weir cylinder(s). In a second and preferred stage, the liquid flow rate is sufficient to fully wet the weir ID, creating a full liquid curtain, but is not so great as to completely fill a cross section of the weir. That is, a gas flow area would still be available down the weir diameter. In a third operating stage liquid flowrate might be so high that a back-up of the liquid occurs, to a point that the weir functions as a submersed orifice.
One problem with using a quench, as discussed above, to cool a very hot gaseous stream by contact with a corrosive liquid, such as is the case with cooling gases from a halogenated material reactor, is in providing suitable materials for the quench vessel walls that will withstand corrosion. Materials must be found that can withstand both the corrosive effect from a hot dry gas environment and also withstand a corrosive liquid aqueous environment. Wall portions exposed to both a corrosive aqueous liquid and a hot gaseous stream are subject to severe corrosive action. Thus, the materials selected for areas of a quench vessel wall that come into contact with a gas/liquid interface are of critical importance. The instant invention provides several methods and apparatus for solving the above materials problems so as to minimize vessel wall corrosion.
In one aspect, the invention includes a vessel for receiving a gas, at temperatures greater than 1100xc2x0 C., and contacting the gas with an aqueous corrosive liquid therein, such as aqueous hydrogen halide liquid. The vessel preferably includes upper wall portions lined with a hot face material. A hot face material is generally known in the art and includes materials such as Al2O3, refractory brick, and refractory materials capable of withstanding hot dry temperatures such as in the range of 1450xc2x0 C. The vessel should include a pressure wall or shell and may include a jacketing over the pressure wall or shell to help control exterior vessel wall temperatures, at least for the hottest upper regions of the vessel. Preferably a quench vessel upper region also includes inner lower wall portions comprised of a carbon based material, SiC material or other non-metal materials suitable for containing a corrosive aqueous liquid.
In one embodiment of the instant invention, a membrane wall is located upon an inner vessel wall proximate a liquid/gas interface level. The liquid/gas interface level in a quench may vary somewhat. However, the level should be able to be predicted to within a height range which may run a few feet for some embodiments. A membrane wall is comprised of tubing that provides internal channels for circulating a cooling fluid. Alternately, a carbon block or ring wall can be located upon an inner vessel wall proximate a liquid/gas interface, with the block providing internal passageways for circulating a cooling fluid, like the membrane wall above. With the membrane or carbon block wall, the inner wall surface remains dry.
In a further dry wall embodiment, a SiC, graphite, silica or similar material block or ring is located on the inner vessel wall proximate, above and below a liquid/gas interface. Contact with the liquid below cools upper portions of the block or ring by heat transfer through the material itself such that wetted portions above the interface remain below approximately 1000xc2x0 C., a temperature at which the material can sufficiently withstand corrosion, notwithstanding contact with the hot gas.
In another embodiment of the instant invention, a graphite ring wall can be located upon an inner vessel wall, proximate a liquid/gas interface level, with the ring in communication with, and having ports for discharging, a cooling fluid therethrough. Such ring and ports are structured to discharge cooling fluid substantially down the inside vessel wall below the ports and above the interface. A graphite ring can include a graphite splash baffle attached to the inner vessel wall and extending inwardly over the ring ports. In an alternate embodiment, the vessel can include a porous seeping ceramic wall (sometimes referred to as a weeping wall) located upon the inner vessel wall proximate a liquid/gas interface level, with the ceramic wall in communication with a source of cooling fluid for communicating a fluid therethrough. The cooling fluid passes through the wall, or seeps through the wall, and down inside wall surfaces, cooling the wall and forming a liquid curtain over inside wall surfaces. Seeping discharge is limited to desired wall surface portions by finishing or coating to an impermeable state ceramic wall surfaces not desired to seep.
In another aspect, the invention includes apparatus for quenching a hot corrosive gaseous stream including a reactor discharging a hot corrosive gaseous stream of at least 1300xc2x0 C., a quench vessel in fluid communication with the reactor for receiving the gaseous stream and contacting the gaseous stream with an aqueous liquid and a means located between the reactor and the quench vessel for cooling the reactor gaseous stream to below 1100xc2x0 C. in a dry environment. The means for cooling can include a radiant cooler, a convective cooler or a dry spray quench.
The invention also includes methods for quenching a hot gaseous stream that includes discharging a gaseous stream at temperatures in excess of 1100xc2x0 C. into a quench vessel, cycling a corrosive aqueous liquid into the quench vessel and cooling vessel wall portions around a liquid/gas interface level with a cooling fluid, the cooling fluid either circulated interior to the wall or discharged over interior wall surfaces. In an alternate embodiment, the invention includes a dry environment method for quenching a hot corrosive gaseous stream comprising discharging a corrosive gaseous stream from a reactor chamber at temperatures greater than 1300xc2x0 C., cooling discharging gas to below 1100xc2x0 C. in a dry environment and communicating the cooled discharged gas to a quench vessel for cooling to temperatures of less than 200xc2x0 C. by contacting the gas with an aqueous liquid.